This application claims benefit of Japanese Application No.2000-215106 filed in Japan on Jul. 14, 2000, the contents of which are incorporated by this reference.
1. Field of the Invention
The present invention relates to a distance measuring device, an optical sensor, and a camera, such as a film-based camera (silver-halide film camera) or a digital camera, having the distance measuring device.
2. Description of the Related Art
Conventionally, distance measuring devices use a distance measuring sensor provided with a plurality of pairs of line sensors to ensure the measurement of a distance to a subject. For example, one of the distance measuring devices can measure the distance within a wide range by providing distance measuring areas having a plurality of lines. In this distance measuring device, as a larger number of distance measuring areas are arranged corresponding to the line sensors, the subject can be certainly photographed, thereby improving the precision of distance measurement.
In the case of applying the above-mentioned distance measuring device to film-based cameras (silver-halide film cameras) having a zoom lens, there is a problem in that, inconveniently, a space between the distance measuring areas widens relatively to a size of a focal plane and a part of the distance measuring areas is out of the focal plane because even if the distance measuring areas are arranged within a wide range of the focal plane in the case of a low photographing magnification, an angle of view upon photographing is narrow when the a photographing magnification is increased.
Recently, compact size is required for film-based cameras (silver-halide film cameras) and digital cameras and, in association therewith, miniaturization is also required for the distance measuring device. Also, there is a problem in that the space between the distance measuring areas widens by using a distance measuring sensor having the same space between photodetector units even if a focal distance of a distance measuring optical system is reduced so as to miniaturize it.
Then, in order to solve the inconvenience of the above conventional distance measuring device, Japanese Unexamined Patent Application Publication No. 11-153751 proposes a distance measuring device in which a photodetector unit and a processing unit form an L-shaped pattern every pixel of a line sensor and a distance measuring sensor is composed of a train of the photodetector units and a train of the processing units to join the patterns of adjacent pixels to each other. In the case of a distance measuring area which is symmetrical in the vertical direction, the photodetector unit of the line sensor having the pattern is arranged to a symmetric axis of the distance measuring area.
However, even if applying the line sensor of the distance measuring device in the Japanese Unexamined Patent Application Publication No. 11-153751, inconveniently, the space between the distance measuring areas is much wider because the processing unit exists between the photodetector units.
FIG. 15A is a diagram showing the arrangement of the line sensor of the above distance measuring device. Referring to FIG. 15A, in the distance measuring device, a distance measuring sensor 201 comprises: a center line-sensor 211; an upper line-sensor 212; and a lower line-sensor 213. The center line sensor 211 comprises a train of photodetector units 211a and trains of processing units 211b1 and 211b2 which are arranged on upper and lower sides of the train of photodetector units 211a, respectively. The upper line-sensor 212 comprises a train of photodetector units 212a and a train of processing units 212b which is arranged on the upper side of the train of photodetector units 212a. The lower line-sensor 213 comprises a train of photodetector units 213a and a train of processing units 213b which is arranged on the lower side of the train of photodetector units 213a. As described above, the trains of processing units are provided between the trains of photodetector units, thus widening inter-trains of photodetector units.
It is considered that an IC process for manufacturing the distance measuring sensor is made fine to reduce the size of a processing circuit unit, thereby further reducing a space between the photodetector units. However, this method has a problem in that costs are increased and it is not appreciable to the cameras.
In a distance measuring device disclosed in Japanese Unexamined Patent Application Publication No. 11-153749, line sensors are arranged linear-symmetrically to an imaginary line, and trains of photodetector units are closer to the imaginary line, rather than trains of processing units. This arrangement causes a space between photodetector units to be narrow.
However, in the line sensors of the distance measuring device disclosed in the Japanese Unexamined Patent Application Publication No. 11-153749, inconveniently, a space of one part of photodetector units is much close thereto, a space of the other part is much wide, and the arrangement of the distance measuring areas becomes unbalanced.
FIG. 15B is a diagram showing the arrangement of the line sensors in the above distance measuring device. Referring to FIG. 15B, in the distance measuring device, a distance measuring sensor 202 comprises: a center line-sensor 221; a lower line-sensor 222; and an upper line-sensor 223. The center line-sensor 221 comprises a train of photodetector units 221a and a train of processing units 221b which is arranged on the upper side of the train of photodetector units 221a. The lower line-sensor 222 comprises a train of photodetector units 222a and a train of processing units 222b which is arranged on the lower side of the train of photodetector units 222a. The upper line-sensor 223 comprises a train of photodetector units 223a and a train of processing units 223b which is arranged on the upper side of the train of photodetector units 223a. As shown in FIG. 15B, the trains of photodetector units 221a and 222a are exceedingly close to each other, and the trains of photodetector units 221a and 223a are exceedingly far from each other., thus exhibiting the asymetry of the arrangement.
To solve the above-mentioned inconveniences, according to the present invention, it is one object of the present invention to provide a distance measuring device having a plurality of pairs of line sensors with low costs whereby the density of distance measuring areas can be sufficiently maintained if a photographing magnification is increased and if a distance measuring optical system is reduced in size, and a distance to a subject can be measured without fail by the proper arrangement of line sensors. Also, it is another object of the present invention to provide a camera incorporating the above-mentioned distance measuring device. Further, it is another object of the present invention to provide an optical sensor having a plurality of pairs of line sensors whereby the density of a detecting area can be sufficiently maintained if a detecting magnification is increased and if the size is miniaturized, and accurate detection becomes possible by the proper arrangement of line sensors.
According to the present invention, there is provided a distance measuring device comprising: an optical system for dividing an image of a subject and forming the image; and a plurality of line sensors arranged substantially onto an image-forming plane of the optical system, each of which has a train of photodetector units composed of a plurality of pixels for receiving light of the subject image which passes through the optical system and a train of processing units for processing and outputting a charge generated in the train of photodetector units, wherein at least one of the plurality of line sensors divides the train of photodetector units into a plurality of blocks, of the train of processing units corresponding to each block, one part of train of processing units is arranged to one side of the train of photodetector units, and the other part of train of processing units is arranged to the other side to sandwiching the train of photodetector units.
Further, according to the present invention, there is provided an optical sensor comprising a plurality of line sensors, each of which comprises a train of photodetector units composed of a plurality of pixels for receiving light and a train of processing units for processing and outputting a charge generated in the train of photodetector units, wherein at least one of the plurality of line sensors divides the train of photodetector units into a plurality of blocks, each of the train of processing units corresponding to each block, one part of train of processing units is arranged to one side of the train of photodetector units, and the other part of train of processing units is arranged to the other side to sandwich the train of photodetector units.
Furthermore, according to the present invention, there is provided a camera having a distance measuring device, comprising: a photographing optical system; a drive unit for driving the photographing optical system in an optical axis direction; an image pickup unit for photographing an image of a subject which is formed through the photographing optical system; a distance measuring optical system for dividing and forming: the image of the subject; a plurality of line sensors arranged substantially onto an image forming plane of the distance measuring optical system, each of which comprises a train of photodetector units composed of a plurality of pixels for receiving light of the image of the subject which passes through the distance measuring optical system and a train of processing units for processing and outputting a charge generated in the train of photodetector units; and a control unit for controlling an operation of the drive unit based on outputs of the line sensors so that the image of the subject is formed onto a focal plane of the image pickup unit, wherein at least one of the plurality of line sensors divides the train of photodetector units into a plurality of blocks, of the train of processing units corresponding to each block, one part of train of processing units is arranged to one side of the train of photodetector units, and the other part of train of processing units is arranged to the other side to sandwich the train of photodetector units.
Further objects, features and advantages of the present invention will become apparent from the following description of the preferred embodiments with reference to the attached drawings.